It is well known that the therapeutic drugs such as α-methyldopa, penicillins and cephalosporins may elicit the positive direct antiglobulin test. But the immunopathologic mechanisms for the positive direct antiglobulin test following the administration of cephalosporins have not been clear yet. It has been suggested that the immune response develops due to adsorption of serum proteins to the red cell membranes affected by cephalosporins.
In vitro studies was performed covering the three aspects of the antiglobulin reactions observed by drug-coated red cells: (1) the minimum concentration sufficient to give a positive direct antiglobulin test, (2) the nature of the serum proteins adsorbed onto the red cell membranes, and (3) thee intensity of the agglutination of cephalosporin-coated red cells with normal serum applied was tested by the method of antiglobulin test.
1) The minimum concentration of five kinds of cephalosporins which gave a positive antiglobulin test was from 1.67 (cephalothin) to 40mg/ml (cefotiam). The intensity of the positive direct antiglobulin test was dependent upon the concentration of cephalosporins employed. On the other hand, penicillins and α-methyldopa employed, no positive direct antiglobulin test was observed. Therefore, no adsorption of serum proteins onto the red cell membranes coated by the above mentioned two drugs might be suspected.
The mechanisms of the positive direct antiglobulin tests with cephalosporins were considered to be different from those of penicillins and α-methyldopa in vitro.
2) No specificity of immnoglobulin class could be detected in the serum proteins adsorbed onto the cephalosporin-coated red cell membranes.
3) The wide range of intensity of positive antiglobulin reactions was largely influenced not by the cephalosporin-coated red cells but by the individual serum used in the test.
The immunopathological mechanisms of this phenomenon might be considered to be nonspecific adsorption of the serum proteins onto the red cell membranes altered by cephalosporins. However, in vitro studies suggested the possibilities of existence of cross-reacting antibodies and specific antibodies to that drugs in the sera of normal population.

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The measurement of anti-HBs antibody potency has been carried out by RIA, PHA (Micro), CEP and Micro Ouchterlony methods. Parallel line assay by RIA method is an established method for the measurement of anti-HBs potency. We have attempted to establish a simple and precise parallel line assay method using macro-titration tubes (Macro-PHA method).
PHA test kit, HEBSGENCELL^® was used for the Macro-PHA method. Three kind of anti-HBs immunoglobulin preparations supplyed by different distributers were diluted with phosphate buffered saline (pH 7.2) and the potencies were measured within 3 days after the dilution. Macro-PHA method was carried out in polystylene test tube (∅ 14mm, U type). The diameter of the hemagglutination ring was measured.
Plots of log (dilution factor) versus log (diameter) were linear between 5.5 and 10mm diameter. The slope of the three different kind of anti-HBs immunoglobulin preparations were in good parallelism stastically between one to the other. Relative potencies of the three kind of anti-HBs immunoglobulin preparations were calculated. The reproducibility of this assay was also confirmed satisfactory.

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